[GRASS-dev] v.clean: dangles removed but nothing cahnged (?)

[Maciej Sieczka]

Hi,

Although v.clean often prints "Removed dangles:   177", nothing
actually changes in the output compred to input. What does that message
actually mean?

in spearfish:

$ v.clean in=roads out=roads_nodang tool=rmdangle

| Remove dangles                  |  Building topology ...
825 primitives registered
Topology was built.
Number of nodes     :   676
Number of primitives:   825
Number of points    :   0
Number of lines     :   825
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   -
Number of isles     :   -
Removed dangles:   177  removed lines:     0
Building topology ...
825 primitives registered
0 areas built
0 isles built
Attaching islands:
Attaching centroids: Topology was built.
Number of nodes     :   676
Number of primitives:   825
Number of points    :   0
Number of lines     :   825
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0

Now run the same command on the previous output - the same information
about 177 removed dangles pops up. Why?

$ v.clean in=roads_nodang out=roads_nodang2 tool=rmdangle
| Remove dangles                  |  Building topology ...
825 primitives registered
Topology was built.
Number of nodes     :   676
Number of primitives:   825
Number of points    :   0
Number of lines     :   825
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   -
Number of isles     :   -
Removed dangles:   177  removed lines:     0
Building topology ...
825 primitives registered
0 areas built
0 isles built
Attaching islands:
Attaching centroids: Topology was built.
Number of nodes     :   676
Number of primitives:   825
Number of points    :   0
Number of lines     :   825
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0

There is no difference between roads_nodang and roads_nodang2:

$ v.build roads_nodang option=dump > roads_nodang.dump
$ v.build roads_nodang2 option=dump > roads_nodang2.dump
$ diff roads_nodang2.dump roads_nodang.dump
(nothing printed)

so the data was not modified, despite "Removed dangles:   177". Or was it?

Maciek

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